Biogenic Sulfide Production in Continuous Systems: Containment Strategies Targeting Microbial Metabolism
Notice bibliographique
Résumé
Abstract Nitrate-and nitrite-mediated containment of souring was studied in continuous up-flow packed-bed bioreactors. Produced water of the Coleville oil field in Saskatchewan, Canada, was used as an inoculum for establishing biofilms of sulfate-reducing bacteria (SRB). With a medium containing 12 mM sulfate and 25 mM Nalactate (10–11 mM produced sulfide), 17.5 mM nitrate or 20 mM nitrite were required for complete removal of sulfide at a retention time of 24 h. During nitrate or nitrite addition environmental redox potential increased gradually from -700 mV to -400 mV, with final values still being in the optimum range for SRB activity Prior to addition of nitrate or nitrite microbial communities in the liquid phase were dominated by SRB. Addition of nitrate or nitrite shifted the composition of community to heterotrophic and nitrate-reducing (NRB) bacteria. Introduction Souring, the production of hydrogen sulfide (H2S) in oil reservoirs subjected to water flooding for secondary oil recovery, is caused at least partly by sulfate-reducing bacteria (SRB). These bacteria use electron donors present in the oil and formation water (organic acids and hydrocarbons) to reduce sulfate to sulfide. The activity of SRB is also associated with increased corrosion risk. Strategies for mitigation of biogenic sulfide production include:removal of sulfate from water prior to injection,application of biocides to inhibit or kill SRB, ormanipulation of microbial metabolism through addition of nitrate or nitrite. The latter approach has been tested in the Coleville oil field, located in Saskatchewan, Canada. Injection of 400 ppm ammonium nitrate for 50 days gave on average a 73% decrease in sulfide concentration in injection and producer wells (1). The control of biogenic sulfide production by addition of nitrite, nitrate, and nitrate-reducing, sulfide-oxidizing bacteria (NR-SOB) and the involved mechanisms have been studied in our recent work(2,3). NR-SOB oxidize sulfide (to sulfur or sulfate) when reducing nitrate to nitrite or nitrogen. To better simulate conditions prevailing in oil reservoirs, a study on the containment of souring was conducted in continuous packed-bed bioreactors with established SRB biofilms. The present paper describes the preliminary results of this study. Experimental system and procedures The containment of biogenic H2S production was studied in two up-flow packed-bed bioreactors, made of a glass column (D: 4.5 cm and H: 64 cm), with 5 sampling ports at 14 cm intervals. Sand was used as a matrix for biofilm establishment. Modified CSB medium (2) was introduced at the bottom of the bioreactors, using tygon tubing and a peristaltic pump. The effluent stream left the top of the bioreactor through a rubber stopper and tygon tubing connected to an effluent vessel. The immobilization of bacterial consortia (mainly SRB) was achieved by initial operation of the bioreactors in batch mode, followed by operation in continuous mode. The bioreactors, containing modified CSB medium were inoculated by injecting 10 mL Coleville produced water at each sampling port. The bioreactors were maintained at room temperature (22 °C). Following complete sulfate reduction, the medium was pumped into the bioreactor at an increasing flow rate (final value 9 mL/h, corresponding to a residence time of 24 h).
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Comment cette classification a été obtenuedéplier
Prédiction machine sur la base complète
Imitation des enseignantsNi prévalence calibrée, ni vérité terrain. Validation humaine à venir. Le volet Gemma est une étiquette directe du modèle pour chaque travail de la base, lue sur la notice réduite au titre. Le volet Codex est un classifieur appris des 10 348 étiquettes directes de Codex et calibré sur les taux pondérés de l'échantillon; les champs sans appui suffisant ne portent aucun appel Codex. Le mode candidate est l'union des deux volets; le consensus est leur intersection. Ces sorties portent le statut machine_predicted_unvalidated et ne sont pas des étiquettes humaines.
Scores du classifieur distillé par catégorie (deux têtes)
| Catégorie | Codex | Gemma |
|---|---|---|
| Métarecherche | 0,000 | 0,000 |
| Méta-épidémiologie (sens strict) | 0,001 | 0,000 |
| Méta-épidémiologie (sens large) | 0,001 | 0,000 |
| Bibliométrie | 0,000 | 0,000 |
| Études des sciences et des technologies | 0,000 | 0,000 |
| Communication savante | 0,001 | 0,000 |
| Science ouverte | 0,001 | 0,000 |
| Intégrité de la recherche | 0,000 | 0,000 |
| Charge utile insuffisante (le modèle a refusé de juger) | 0,000 | 0,000 |
Scores machine (provisoires)
Les deux têtes enseignantes du modèle étudiant, lues sur ce travail. Un score ordonne la base pour la relecture; il n'affirme jamais une catégorie, et le statut de validation accompagne chaque rangée tel quel.
Scores de référence d'un modèle non mature (critères de maturité non atteints, 7 itérations). Un score ordonne; il n'affirme jamais une catégorie.
score_only:v0-immature-baseline · tel quel depuis la passe de notation : score_only signifie que le nombre peut ordonner les travaux, et qu'aucune étiquette de catégorie n'en découleClassification
machine, non validéePrédiction automatique; un appel candidat d’une seule source (Gemma direct ou Codex distillé), pas un consensus.
Le détail, modèle par modèle et score par score, se trouve en fin de page sous « Comment cette classification a été obtenue ».